The present invention relates to a printing apparatus of the type wherein a print wheel is presented to a hammer mechanism for printing of a character upon paper or other sheet material.
It is known to use a print wheel to print characters upon paper or other sheet material. The print wheel can take the form of a daisy wheel wherein a plurality of type-bearing fingers are held in and elastically restored to the plane of a central supporting disc, or to take the form of a type wheel where the fingers are elastically supported at an angle, typically 90.degree., to the plane of the central supportive disc. The print wheel is rotated until a desired character falls beneath a hammer mechanism which is operated to cause the hammer, selected typeface character and ink ribbon to come together onto the paper to leave a printed record.
In the prior art, a printhead assembly was first positioned where the character is to be typed or printed and the daisy wheel either thereafter or simultaneously with the printhead positioning is rotated until the desired character is under the hammer. The hammer is then operated to cause the above described printing operation. Separate motors are required to position the print wheel and to position the printhead assembly. At least one of the motors is required to be situated on the printhead assembly, severely limiting the degree of miniaturization possible in such a printer. The daisy wheel or other print wheel is required to accelerate and decelerate in two directions, thus inducing bi-directional stress in the daisy wheel or print wheel rotating apparatus.
The present invention seeks to provide improvement over the prior art by providing a print wheel printer wherein only a single motor is required both for the positioning of the printhead assembly and for the rotary positioning of the print wheel. The present invention seeks further to provide improvement over the prior art by allowing for the single motor to be positioned away from the printhead assembly, thereby allowing for miniaturization of the printer to permit the use of a print wheel or daisy wheel printer in those situations where previously only a low quality dot-matrix printer could be used.
In the prior art, controllers were provided for a print wheel printer wherein the print wheel was rotated bi-directionally towards a desired printed character being beneath the printing hammer. The present invention seeks to provide improvement over the prior art by allowing the use of a controller where the print wheel is rotated uni-directionally between successive printing operations, thereby allowing by a simple process the enciphering and deciphering of documents such that they may readily be prepared and read but cannot be rapidly deciphered without knowledge of a simple deciphering key and without use of such a uni-directional controller.